The present invention relates to sound-damped saw blades. More particularly it relates to sound-damped saw blades employing a viscoelastic damping layer on one major face thereof.
Sound-damped saw blades of the type employing a viscoelastic damping layer have been previously described. See for example U.S. Pat. No. 3,799,025. Generally such blades employ a rigid sheet over the viscoelastic layer, the combination often being referred to as a constrained-layer damping device.
Constrained-layer damping devices have been quite effective in substantially damping the vibration responsible for the loud and objectionable whine or sound emitted from circular saw blades during operation. However, saw blades employing such devices have not proven entirely satisfactory in use in the lumber and wood products industry. For example, wood pitch quickly builds up at the peripheral edge of the constrained-layer damping device where the viscoelastic layer meets the saw blade. As a result, the thickness of the edge increases and eventually causes the damped blade to bind during normal use. This in turn causes the damping device to be torn away from the blade. Additionally, the resonant vibration encountered during use of the blade causes the damping device to repeatedly strike the material being cut. The combination of the rotation of the blade and this striking action causes the exposed edge of the damping device to dig into the side of the cut being made and raise the device from the blade. Moreover the rigid sheet of such devices has sharp corners on its exposed surfaces. This increases the tendency of such devices to dig into the side of any cut being made.
The present invention overcomes these disadvantages of the prior art by providing an abrasion-resistant edge coating around the edge of the constrained-layer damping device. Despite being highly resistant to abrasion the edge coating provides a lubricious surface to those materials being cut by the sound-damped saw blade. The novel edge coating seals the edge of the constrained layer damping device, prevents the build up of wood pitch at said edge and prevents the edge from being torn away from the blade. Consequently the improved sound-damped saw blades exhibit increased useful life. Moreover, in a particularly preferred aspect of the invention, the constrained layer damping device is provided with a tapered shoulder at its outer circumference.